1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a portable liquid crystal module.
2. Discussion of the Related Art
In general, flat panel display devices are thin, light weight, and have low power consumption. Thus their application in portable devices is increasing. Among the various types of flat panel display devices, liquid crystal display (LCD) devices are widely used for laptop computers, televisions and desktop monitors because of their superiority in resolution, color image display, and display quality.
LCD devices make use of optical anisotropy and polarization properties of liquid crystal molecules to generate a desired image. In particular, liquid crystal molecules can be aligned in a specific orientation by controlling the application of an electric field across the liquid crystal molecules. Due to optical anisotropy, incident light is refracted according to the orientation of the liquid crystal molecules, thereby generating the desired image.
FIG. 1 is a perspective view of a liquid crystal display device according to related art. In FIG. 1, the liquid crystal display includes a liquid crystal panel 10, a backlight assembly 20, a top case 31 and a rear case 32. Although not shown in FIG. 1, the liquid crystal panel 10 includes two substrates with a liquid crystal layer disposed between them. The backlight assembly 20 is positioned under the liquid crystal panel 10 and functions to supply light to the liquid crystal panel 10. The top and rear cases 31 and 32 accommodate and fix the liquid crystal panel 10 to the backlight assembly 20.
There are two types of backlight assemblies 20, an edge type and a direct type, based on the arrangement of the light source within the liquid crystal display device. In particular, an edge type backlight device has a light source installed at one or both side portions of the light crystal panel 10, and a direct type backlight device has a light source installed underneath the liquid crystal panel 10. Usually, laptop computers adopt the edge type backlight assembly in order to reduce their size and thickness. However, televisions and computer monitors adopt the direct type where the light guide plate and some prism sheets are omitted for the purpose of raising the brightness thereof. For example, the 26-inch television includes sixteen cold cathode fluorescent (CCF) lamps, as the direct type. The backlight assembly 20 further includes functional optical films, e.g., diffusions sheets, as well as lamp(s).
FIG. 2 is a sectional diagram illustrating an edge type backlight assembly according to related art. In FIG. 2, light emitted from a lamp 21 passes through a light guide plate 22. The light guide plate 22 guides the incident light toward a diffusion sheet 25 and other optical sheets 27. The linear light emitted from the lamp 21 is converted into surface light by passing through the light guide plate 22, the diffusion sheet 25 and optical sheet 27. The backlight assembly includes a reflector 24 provided underneath the light guide plate 22 to reflect the light upwardly, and the light guide plate 22 includes a plurality of micro-patterns 22a for increasing the reflective efficiency.
However, since the liquid crystal display device includes both the liquid crystal panel and the backlight assembly together, the liquid crystal panel may be damaged by heat emitted from the lamp of the backlight assembly. For example, the circuits of the liquid crystal panel may become broken, and the inverter may malfunction.
Additionally, when the light guide plate is formed to be thin for the purpose of obtaining a thin LCD device, the lamp is also formed to have a small diameter with reduced capacity. Therefore, the optical sheets need to have a good quality of improved light-passing efficiency and may be high in price.